Research ArticlePID controller auto-tuning based on process step response and damping optimum criterion

•FOPDT model may not accurately describe process dynamics for PID controller tuning purposes.•PID controller tuning is based on PTn process model and damping optimum criterion.•Proposed tuning method results in straightforward adjustment of closed-loop damping and response speed, also being relatively robust to process parameter variations.•PTn model on-line identification is based on single integration of process step response.•Process model identification and related PID controller auto-tuning are verified by extensive simulations.

This paper presents a novel method of PID controller tuning suitable for higher-order aperiodic processes and aimed at step response-based auto-tuning applications. The PID controller tuning is based on the identification of so-called n-th order lag (PTn) process model and application of damping optimum criterion, thus facilitating straightforward algebraic rules for the adjustment of both the closed-loop response speed and damping. The PTn model identification is based on the process step response, wherein the PTn model parameters are evaluated in a novel manner from the process step response equivalent dead-time and lag time constant. The effectiveness of the proposed PTn model parameter estimation procedure and the related damping optimum-based PID controller auto-tuning have been verified by means of extensive computer simulations.